This invention relates to a new chemical process, more particularly to a new method for methylating aromatic hydroxyl- or thiol-containing compounds. The resulting products obtained by the instant process have various uses as chemical intermediates, as heat transfer media, as herbicides and in other industrial applications.
In the past, aromatic ethers have been produced by alkylation of the phenoxide ion usually generated by treatment of a phenolic compound with a base such as sodium hydroxide followed by treatment with an alkyl halide, sulfate or sulfonate. The process is disfavored for commercial use because of the formation of metal salt by-products.
Alternate processes which do not form unacceptable by-products are also known. Direct alkylation of phenols by treatment with diazomethane, tetramethoxymethane or pentamethoxyphosphorane, have been previously disclosed in the art. Other processes involve treating phenol with methanol in the presence of dicyclohexylcarbodiimide or a mixture of diethylazodicarboxylate and triphenylphosphine. These processes have proven to be rather inefficient, uneconomical or ecologically unsuitable.
A suitable methylating process which avoids the disadvantages of prior art methods is desired.